Sci­ent­ists have come up with a way to make whole brains trans­par­ent, so they can be labelled with molecu­lar mark­ers and imaged using a light micro­scope. The tech­nique, called CLARITY, enabled its cre­at­ors to pro­duce the detailed 3D visu­al­isa­tions you see in this video. It works in mouse brains and human brains; here the team use it to look into the brain of a 7‑year-old boy who had autism.